US1996053A - Process of cooling - Google Patents

Description

April 1935- G. BLACK ET AL PROCESS OF COOLING Filed 0012. 21, 1932 2 Sheets-Sheet 1 [n mentors 9:. (Black L. 6. BLACK ET AL PROCESS OF COOLING April 2, 1935.

Filed 001;. 21, 1932 2 Sheets-Sheet 2 Inventors Attorneys Patented Apt; 2, 1935 Calif.,}assignors to American Potash & 'Chemical -Gorporati0n, lrona, Calif a corporation =01- V Delaware ApplicationYOctoberIZl,

I r 29 Claims,

This invention relates to the art of cooling and includes improvements applicable to both cooling .lprocesses which. there .is .an indirect. trans .':ter of heat, such as through 'heati exchangers-and processes in which the transfer of heat'is direct, as in barometric =or jet condensers; italso includes features which lare-ofr-particulars value in evaporative' cooling operations .where the cooling medium .is brought into. either direct or indirect contact with the vapors evaporated in the: cool v ing operation.

' a processor 'crystallizing "Glauher salt from :a

solution of sodiumisulphate while simultaneously converting Glauber salt toran'hydrousisodimn sulphate an'd recovering the refrigeration re quired for the crystallization of Glauber salt.

The present inventionincludes i primarily the discovery that if ina processof yc'coling materials a cooling medium is used 'consisting'of certain sludges of solid materials and solutions thereof both the temperature of coo'lingmay be brought more readily toa desired point and this temi-v perature may be maintained more easily constant than with cooling processes heretofore .known, more particularly, if. a sludge is employed as a cooling medium which contains suchcomponents and phases as to have, according to the phase rule, no degrees of freedom. It may "-be employed as a cooling medium' either in .an indirect or. direct manner without varyingzintemperatune during the cooling operations. Thereare various sludges .y

of this class which may be used, Such a sludge should preferably be'one which possesses the fol,- lowing characteristics: I j w 3 1 First, that the solution of the solid .rnaterial in the sludge or the solution of suchmaterial together with the conversion thereof to and the precipitation of another form of (said materialgis an endothermicchange, so that the sludge may absorb heat from the medium to1be cooledwithoutdeviating from its transition temperature;

Second, that-there be sufficient of the solid 1932; serrat 1 38,9321: (c1. 23-1) materialslpresent so, as to retain all solid phases present after the absorption. of the des red amount, of heat and that the system be one haying no degrees. of freedom, andin addition thereto where-the .cooling medium is employed in direct contact: with vapors; and: "the materials being cooled, the, cooling i medium contains sufficient of-gsuch solid materials tosaturate :the new solvent condensed. 1 1 A preierred example oflsuch' a sludge suitable in our process, -of-cooli-ng is'gone consistingof a saturated solution of salts. inequilibrium with two salts of different degrees of hydrationyone .of .the degreesjoi ,hydrationmayJbe:zero, as in the ;case of anhydrous salt, or both of thedegrees of hydration may represent; hydrated salts, one having a'higher degree of hydration than the other.

Forvexample, a solution :ofsodium sulphate at 1 the temperature of transition between thedecahydrate @(NazSOLlGI-IzO) tel-sodium sulphate anhydroustNaaSOQ containing; .an excess of both solids is asludgesystemi possessing no degrees offreedom; This sludge may absorb heat when brought into direct or indirect contact with the material; to. be cooled without varying in temperaturebecausejthe heat absorbed ,is consumed in effecting a-tra-nsitionoi the more hydrated salt to the less'hydrated salt, c

A further *31dV3l-Ill12t3810f the use of such cooling.

mediums-in-the present invention resides in the fact; that the j'tempenature atrwhich they exist and at which they maintain themselveszinth'e.

cooling operation is in many cases lower thanthe temperature at which coolingwater itself may be obtained in many regions. -'Ihus, for'example, the transition temperature of the particular sludge --described is:-32.38i- C. sludges having no :degreesof freedom may readily be formed, which possess even "lower transition temperatures. Asya simple example thereof, by

u-Other cooling adding common salt to such :a sludge the trans'igtion temperature of thesludgewmay be depressed lower cooling temperatures, -when,emplo yed in prevalent particularly fin summer months; are

such that spray pond water; can n'o'tbe obtained at .-temperatures below; about 25 to 30; C.

:volves the application oftheprinciples of' a con- Ihe-process of the present invention has,'there;-' :fore, special advantages in its abilityto maintain deserti-regions. Indesert regions'the"conditions",

Alfurther featureof the present invention in- Lstant temperature :cooling sludge to the recovery, 7

of a salt of low degree ofhydration from a higher hydrated form got said-salt. In particular, the

, by the cooling medium sludge causing *the con- 1 version of the higher hydrate to the lower-hydrate.

invention-is applicable to the recovery ofany salt in a form'having a low, degree of hydration from which the transition from ahigher hydrate to a lower hydrate is endothermic. Briefly, the recovery is accomplished byfirst crystallizing out the higher hydrate, forming a sludge on said" hydratewith a substance capable .of depressing the transition point between said higher hydrate and the desired lower hydrate and employing such sludge as a cooling medium to cause crystalliza-l tion of further higher hydrate, the heat absorbed The present invention, together with various other objects and advantages thereo Particularly certainadvantages discovered in connection with one particular applicationzof the inven'tion,;will best be understood from a description of particular forms or examples of processesembodying the invention. For this purpose, we have hereinafter described in detail preferred rormsof our process. The description is given with reference t h c panying drawings, in which adapted for use ina second form V Figure 1 represents an elevation-'ofan apparatus' adaptedfor carrying'out'one form of the process embodyingthe invention; and I Figure 2 is an elevation showing an apparatus of the process embodying this invention. I

Referring, first, to Fig. *1 of'the drawings, the

apparatus there illustrated comprises an evapo-- V rator l of any suitable form, having 'top' and bottom closures 2 and 3. "Preferably, there is provided as'uitable means foragitating the cbirtents of the evaporator, such" as the: circulation 'system comprising the circulating .'lines- -4 and 5 and pump 6. 'There is also provided a valved inlet line 1 for the material to be cooled and'a I valved outlet-line 8,"in case it is desired to "operatethe process 7 and apparatus continuously;

Leadingfrom the top of the evaporator l is a vapor line ,9 which leads to abarometric condenser In which is provided with the usual tailpipe l l leading to hot well I2,:from which admixed'cone densate and cooling medium" may be; withdrawn, if desired, I through line l3. The hot well serves as a'sealfor'the barometric condenser' III. A valved inlet line I4 is provided at the-upper end "of the barometric condenser I for'introducing the cooling medium, and the barometric ,con-, denser is also preferably provided with a line. l

,leading to a suitablemeans for removing noncondensible gases. 7 In the operation of the process and apparatus,

\ the solution to be cooled may be continuously introducedinto evaporator I by line land continuously removed'therefrom through-line 8. In operation, it ispreferably agitated by circulation through lines 4 and- 5 by pump'6.' Upon the evaporator I there is imposed a pressureless than atmospheric so as to cool the'niaterial therein through'removalj'of heat of vaporization and the vapors arepassedthrough line 9 intocondenser H). In the condenser I 0' the vapors are ,preferably brought'into direct -contact'with the "cooling mediumentering the line H and are thus condensed and pass out' admixed'with the cooling medium through the'tail pipe -ll' into the hot'welllli {In the operation of such process the temperature of cooling in theevaporator- I is dependent upcnthevapor' pressure, and, in

turn, the temperature of the-cooling agent and condensate introduced into-the ba'ro'metric condenser I0 through line I4.

The present invention provides a means by pressure essentially operations: a "For the condensing medium introduced into 'which this temperature maybe maintained more; readily constant and also lower in certain cases" than has heretofore be'en'economically possible with this type of cooling apparatus. When such a type' of barometric condenser is serviced with cooling water, such as spray pond cooling water,.

the temperaturev reached 1 in the barometric condenser is dependent uponlwhat' temperature can .be secured from the spray ponds. Frequently, 1 lower temperatures than this are desired. "Moreover, when a condenser of this type is serviced with spray water, the temperature rises in the condenser'due to, contact withthe vapors to be cooled, and depending upon the, rate of supply of coolingimedium andthe rate of evaporation in the evaporator lconsiderable fluctuations in temperature may'arise' at difierent times. The

present invention is intended to obviate both of these difficulties by using as acooling medium j introduced in the line H a medium which can bemade and supplied at a lower temperature than spray pond water-and also one'which will maintain its Ptemperatureyand also the vapor 'constant' throughout theg H, E

line N we prefertoemploya sludge containing anexcess of one or more, salts, which sludge possesses no degrees of freedom. Theexactmaterials employed in making such a s'lud ge I. will, of course, vary with the diiferent materials which can be economically obtained. Their chemical nature is immaterial, provided they are sumcientlysoluble to'produce the desired sludge and to produce a sludge at the desired temperature.

It is preferable, however,-that thesaltu'sed-be one having at least. two degrees of I hydration. For example, weprefer to employiin the process salt solutions containing primarily 'sodiiimsul phate, since this ingredientfis one of products obtained in the evaporation of -Searles Lake brine. Sodium sulphate and common salt-can;

be obtained from waste products from Searles Lake brine byfthe processes described in the following patents: Allen et al., Patent'No.]1-,8'73,251,

issued August 23, V 1932; MacDonald'et 'al.,*'Pat'ent No. 1,810,181, issued June 16, 1931. A preferred cooling medium might thus 'fb'e made by dissolvingsodium' sulphate decahydrate in water.. 'I'heheatioffsolution ifirst coo'ls the admixed sludgefthusvobtained, and the temperature eventually reachesthe transition 'temperature between the decahydrateor Glauber salt and ,7

anhydrous sodiumsulphate; when sufiiciehtan- .hydrous sodium sulphate has been produced to cause its precipitation;- Provided"suf ficient"so- ,dium sulphate decahydrate is, employed, a satuperature or pressure ofthe' medium within-'the condenser I 0. The heat is absorbed'by-thehe'at and by the dissolution ofysolid decahydratez As of transformation :of the decahydrate salt" to. I the anhydrous'salt during the cooling operation long as heat is being absorbed, sodium sulphate decahydrateis converted. to anhydrous sodium sulphate; Suflicient excess decahydratesalt' should be present in the'sludge'so .as'to permit such continued 'absorptionof heat and also to ncomes saturate any condens'ate ofwaporsamine evaporator .1 with sodium sulphate. In this manner; the process of the present. invention avoids any irregularities .1 in' the pressure maintained' on the evaporator I- 'or' the temperature ofcoolingin evaporator l and:.thei cooling process thus maybe operated'without speciarattention as to the control of rates of flow.

In case a lower temperature of. coolingisldesired in the evaporator l. or'thercooling mediuimin condenser Hi-is desired I to bemaintained atv 'a lower temperature, thisv ma -be accomplished by 'adding'to' the sludge a material capable ofldee pressing the transition temperature between two forms of the salt used. having: different: degreesxof hydration. .As ansexampl'e of anagent which may be addedto" the sludge to lowerithetransition point of sodium sulphate; decahydrate to:- anhydrous" sodium sulphate; we have employed sodium chloride, orcommon salt. Sufllcient common salt, in such -a.-icase, is addedtcthei cooling solution to saturate the? solution' -and at the same." time where as here the cooling medium is employed for direct "contact with the; medium "to" be. cooled an excess of sodium chloride. is provided sufiicient I tained therein.v .Inthe condenser I 0,. with this second type of cooling medium, the temperature is maintained constant independent of the absorption of heat and condensation of.vapors therein so long aszboth the sodium. sulphate: decahydrate and sodium' chloride remain present as solid phases. This cooling' medium containing sodium chloride, as well as thetwo sodium sulphate'salts in the sludge, is of especial'value in cooling brines in desert regionswhere cooling water-of sufliciently .low temperature is oftennot economically available. j I v I As. examples of. other sludges which; form systemsiwithno degrees ofifreedomand'may, therefore, be used as cooling-agents in this process,

may be mentioned solutions of. sodium carbonate at the transition point between the decahydrate and the monohydratewhichis 32?; C. Such a solution is produced byaddingsodium carbonate towater. 1 1" x I A further example is the solution of sodium tetraborate at the transitiomtemperaturebetween the decahydrate and pentahydrate,- which is 60 C. Such a solution could be obtained by adding borax to water. In case of any of the sludges above-named, the transition temperature of. the sludge and thus the temperatureisof cooling inthe process may bemodified by adding to the system an excess of aningredient for altering-the transi .tion temperature. Sodium chloride would-be suitable in all cases, as Wellesv certain other salts. The depression of transition point by theaddition of sodium chloride-is especially great inthe case of these hydrates of sodium tetraborate, theztransition temperature in. a saturated solution, of sodium chloride being about 35 C'.\-

In case of the sludges formed from sodium sulphate and sodium carbonate, both-the conversion of cthehigher hydrated form to-the formof less hydration, and theicrystallidation of the less drated form'are endothermic reactions; soithat the. coolingsludges formed; from these materials and water have-.maximumheat' absorbing capacities. :In thecases-of the slud'gesiormedfrom borax Z: and water, the'solution: of the .decahydratel is ene dotherm'ic, but; the 'crysta'llizationof the ptntahydrate is1exotherinic; "Such;asolutionpossesses a heat absorbing propertmsince;ther'heat of solution of the decahydrate. is appreciably greater than the heat of. crystallization of the pentahydratex and-the capacity'iisequivalent to the difference between thesestwo heatssr1211.

I The temperaturezofthe/condens 'gm'edium will remain constant. atL-the: transition-temperature only'so long as both hydrates are present in the solid. state. If? the cooling medium; is maintained in. contact one:- solid. phase-is entirely on sinned, furtheiuabsorptionjof heat will result in a temperature of the cooling medium. In certain cases, itmay be permissibleand desirable in. the processrtotpennit' inthis manner a slight rise in. temperatureqin'i the cooling medium. Where only one solid. phase'is" present; the temperature of the medium will maintain "constant, however, if the concentration of the two hydrates in theimediumis maintainedconstant. 'Thus, if employed'iin" ansindirect' coolerwhere there is no further dilution, I certain-rsaltsawhich completely melt in. their ownfiwaterof:crystallization may be used in accordancewithi the-process of this invention.as-constanttemperature cooling mediums. For example :by-..exchanging5 heat; in an indirect coolerbetween a medium-to be; cooled and a salt which goes into solution initsown water of crys .tallization, a constant temperature will be..main tained until the salt,has;.entirely,melted.

In the. case of salts which .almost,. but do not quite; melt. in their own-water of crystallization, such as sodiumsulphate, deoahydrate and sodium carbonate decahydrate; the temperature will remain substantially constant throughout .the melting ofthe solid; phase.

In addition to sodiumchloridenas a means for depressing thefltransition temperature of the sludge formed-irornt-sodiumsulphate in water or sodium carbonate inzawater, various other agents may'be employed. For example, sodium hydroxide depresses-the transition point between the'twov hydrates-of sodium-(carbonate as fol-' lows: .1v

.Z; NaOH. in Transitionsolution point oft; I $5.3m.

0:6 '.a5.0-O. 7.9 I same ..v 12. 7, 25. 0 0." a 19.4 mo e If suchv a. medium'cisl employed for reducing the transition temperature, the temperature of cooling in the process of Fig. 1.,where thevapors from the evaporator are condensed" inthe'cooling me-, dium, wouldyary slightly v operation due to. the fact that the sodium:Fhydroxide.concentration. wouldbe undergoingdilution. Such variation, however, would: be at times desirable'jor might be avoided by adding sufficient sodium-hydroxide to' the condensing :medium; to maintain its concentrationconstant;.. if

In some chemical :processes a, hydrated saltis obtained at. one. stage f;v theflprocksss, while a less. hydrated saltqor anhydrous? forniof the salt is desired at a later period in theiprocess. 1

the dissolution of the highenhydrate and subse 4- I I In such cases; it isthe'common practice toieflect quently crystallize. 'out the desired form. Processes of this nature aredoublywasteful in that refrigeration is required to'eflect the. primary crystallization and that heat is added ;tore-dis*- solve the crystallized salt. Thejprocess. of this invention enables these difliculties hto be overcome in anovelmanner.

In order to i1lustrate.this, the rocess of this invention will bedescribedasitis applied to the recovery of sodium sulphate fromsodium carbonate complexes inaccordancewith the process described in the'patent to Allen et al., No. 1,836,-

426. In the process described :in that :patent Glauber'salt is'crystallized by digesting a' mixture containing hydrated sodium :carbonate.'and1.:a double salt of sodium carbonate and sul phate with'water at a:temperaturebelowapproxe imately. 25 C. This Glauber salt:is then re-dlssolved; as by steam, and evaporated toQcause crystallization of anhydrous sodium sulphateuum crystallizer serviced with-abarometric condenser in which a coolingm'edium comprising a sludge of Glauber salt in asaturated' solution'of sodium chloride is I employed. As heat it taken up by the sludge inthecondenserpadditional Glauber salt is dissolvedand part of the dissolved i h I I able settlers. ,The sludge from the latter. is

Glauber salt is changed to anhydrous sodium sulphate. "When a solution saturated with Iboth Glauber salt and anhydrous sodium sulphate is reached, the dissolution of additional-Glauber salt causes the crystallization 'of'anhydrousfsodium sulphate. In this manner, the heatgive'n oftby the crystallization of the Glaubersalt in the vacuum crystallizerisI-takenup in the condenser by the dissolution thereoi and bythe crystallization of the anhydrous sodium sulphate, boththe latter reactions being endothermic; I

This process will be more thorou'g'hly understood from a description of the process as it is i 3 carried out with reference to the apparatus shown in Figure 2- of-the: drawings.

Referring to Fig. 2. there is showna vacuu crystallizer of the type disclosed in a copending application, Serial No. 631,792; which comprises a cylindrical shell [6 provided with-suitable top and bottom enclosures l1 and JB and including a vapor space I9. and-a circulationwell- 20. A large diameter slow-speed impeller 2| provided adjacent and between the bottom of the well 20 and the bottom enclosure l8 causes circulation of the medium being cooled up the outside of and 60 down through'the circulation well 20." Vapors pass from'the vapor space l9and 'through vapor outlet 22 and vapor line. 23 to a suitable barometric condenser 24. A-non-condensible gas outlet 25 is preferably provided near the'topjof the con-'- denser. The": condensing medium "is introduced through a line26 nearthe top'of the condenser.

This condensing medium;preferabiy comprises a sludge of a hydrated salt in a suitable solution,

so that the transition point ot'the system in the condenser is below the crystallization temperature of the Glauberxsalt in the crystallizer. A

sludge of Glauber'salt'in a saturated solution of sodium chloride fulfills these conditions and has been found satisfactory for use as the condens ing' medium. 2

To this end-the Glaubersaltproducedinthe shell 16 is removed as-asludgethrough-an outlet 21 and passed to asuitablearrangementfor re- 7 moving mother liquonas a vacuum filter 28." The filtered salt issluiced. up with end liquorin a well and transferred to a'storage tank or digester '30 in which additional water and sodium deem it advisable. to .allow .a margin of; safety by using a sludgewhich will still contain from -.-10%

- unconverted Glauber salt and from 4.5% undisr,

must be determined empirically, Inrpractice, we

solved sodium chloride. .Inthismanner, a'constant temperature throughout. the condenser -is In our arrangement, .the usual hot-well used with a barometric condenseris replaced by a suitable tank 3!. containing agitating means for maintaining the anhydrous sodium sulphate and remaining sodium chloride and Glauber salt in suspension. 'A circulation'well 32 and an impeller 33 serve this latter purpose. r a

After passing through the condenser, the condensing medium is transferred partially to the digesting tank 3|] for: admixture with fresh sodium chloride. and Glauber salt and partially to a suit- 1 Y sent to the refinery while the clarified liquor is V sent to the Glauber salt filter sludge well 29* for sluicing the Glauber salt'to the'sludgedigester 30. By the userof a Glauber salt-sodium chloride sludge in accordance with these features of our invention, we have found that approximately 88.5%01 the heat given up during the cr'ystallization of the Glauber salt will be absorbed by the condensing medium without addition of any other refrigeration. The balance of the heat of crystallization of the Glauber'salt-may'beconveniently removed by using a primaryrefrigerant serviced surface condenser in the barometric condenser,"as described in P copending application; of Burke et al., SEITNO. 433,984. -To this end am:

barometric condenser. a

moniacoils 35 are employed in the top of the" heat balance obtained by theuse of the Glauber salt-sodium chloride sludge as a condensing'medium is'ide'pendentupon an appreciably lower transition temperature in the system,

Glaubersalt-anhydrous sodium sulphate-sodium chloride water, than, in the same'system free of g sodium chloride andcontaining sodium carbonate.

Thetransitiontemperature between Glauber salt and anhydrous sodium sulphate, in the absence of other salts, is 32.38" C. This transition temperatureinthe presence of sodium carbonate :and burkeite, which is the crystallization tem peraturein the vacuum crystallizer l 6, isjapp'roximately 23 C} In the presence of sodium-chlo- 1 ride, howevezfithe transition temperature of the first-named system 1 drops to approximately 17.9"

C. It is thus possible to secure'an'amount of refrigeration equivalent to the difference between 23 Crand 179C. 'When used in a barometric condenser servicing a vacuum crystallizer, an additional advantage is obtained, as set forth in .U. 5. Patent No. '1,873,329. This advantage arises from the low vapor pressure' of theGlauber salt sludge, due to which it is possible to cool water to a temperature below that of the sludge.

Theinvention, however, is not limited to use with vacuum: cooling equipment, as the temperature effects other than vapor pressure eifectsmayequally .well be accomplished ,withsurface, condensers; Thesludge may, for example, be used asthe cooling medium in either a double'tube orjBaudelot type of heat interchanger. In these latter. cases, the operation will I still be at the transition point between the other solid phases so long as, suflicient of the higher hydrate and=of the depressing component remain tomaintain saturation. If there is a deficiency of the depressing component, the transition temperature,

however, will gradually rise due to dilution of said component. Where a deficiency of both components exists, the temperature of the medium will not remain'constant, but it will .still'be serviceableas a cooling or. condensing medium of high] heatabsorbing capacity. r

Whilewe have described the invention in its preferred forms, it is to be understood that 'various modifications and, changes may bemade, all

within the scope of the-invention as shown in the accompanying claims.

Weclaim:

1, A processoi cooling which comprisesxtrans-v ferring heat from a material to be cooled to a.

sludge comprising an excess of salt in a solution thereof; the systemhaving no degrees of freedom, whereby the absorptionof heat by the sludge is obtained withoutv altering the temperature of the sludge.,- 1. v

32. .A process of cooling which comprises'transferringheat from .a material to be cooled to a sludge'comprising an excess of salt in a solution thereof, the solid phases of said sludge system being salts and including at least two forms ofdif ferent degrees .ofhydration of one salt, said .system having .noidegreesof freedom, whereby the absorption of heat by the sludge is obtained withoutaltering the temperature of the sludge.

, :3.' A process of icooling which comprises transferring heat from a material to be cooled to a sludgecompn'sing an-excessof salt, having at least twodegrees of hydration, ina solution thereof, the :system' having--no degrees of freedom, whereby the absorption of h'eat bythe sludge is obtained without altering the temperature of theslud'ge'.-. r, din-process of cooling, whichcomprisessub- ,jecting the solution to be cooled to'evaporative cooling while passing the vapors of such material to be cooledl into direct contactwith a-sludge havmg no degrees of freedom and" suflicient excess solid'matter present as to maintain all phases present and absorbheat from-and condense said vapors without-change in temperature ofgthe sludge.

'5. A process of cooling,-which-includestrans ferring heat from the material to be cooled to a sludge consisting of asaturated solution'of a salt in the presence of the solid salt at'two different degrees of hydration, whereby heat is absorbed by.

such sludge in converting the higher hydrated salt toalower stage of hydration without substantial alteration in temperature of the sludge. I f

' '6. A process of cooling, which includes 'subject ing asolution to be cooled to .evaporative cooling whilefp'assing the vapors of such solution to ,be coole'dinto direct contact with a sludge consistil l Of .a saturated solution oisalt at the transitionemper e e we chemes of are temperatureofsuch sludge.

.7. .A process of cooling, \irhich includes trans-i ferring {heat from,-the-;material to be cooled to; a sludge oonsistingwofa saturatedsolution ofsalt in the presence of two solid-phases ;,of said saltat different ide i ts of hydration, the sludge containing -.also ,aeonst'rtuent adapted Ito lower p as the transition temperature of such solid of said salt 8. A process of v jecting asolution to beco oledtto evaporative cooling while passingthe vapors'into direct contact with the cooling-and condensing sludge, comprising a saturated solution ofsalt in the presence, of twosolid phases of said salt at different degrees of hydration,-the sludge containing also an excess of a. .constituent adapted to lower the transition temperature ofsaidphases of difierentdegreesof on nl e d e 9. ,A process oi cooling, which comprises sub c ooling which comprisessub- Samar different-degrees :of hydration, whereb y said vapors are condensed without altering the I jecting asolutiontobecooled to evaporative cooling while passing the vaporsinto direct contact; i with acooling and condensing sludge, comprising a, saturated solution of; a salt in thepresence of two solid phasesof, said saltlat diiferent degrees of hydration, the sludge containing, also an excess" of ,-a constituent :adapted to lower the transition temperature of, said solid phases in thesludge',

there being present sufiicientof all the solid Phases; so that both the vapors ,from the liquidto I be cooled maybe saturated with said solid phases and the heat-absorbed without more than consuming any; oneof, said. solid phases.-v

. 110. A process ofcoolingiwhich includes transferring :the heat from themedium-to be cooled to a refrigerant comprisingqa, sludge including a hydrated salt and a lesshydrated salt, in

which the conversion of the, hydrated salt to, the less hydrated form, is an endothermic reaction.

11. A process of cooling and condensing vapors, which includespassing the vapors into contact with a. cooling medium comprising, a sludge con: taining a saturatedssolution of a salt andtwo solid phases thereof at different degrees or hydra-v tionand having nodegrees-of freedom the conversion ofgthe more hydrated tothe less hydrated solid phase of said being an endothermic reaction, suificientof the solid materials being present .to;saturate ,thecondensate. g

,-,;12. ,A processof cooling and condensing vapors,

which comprises bringing the vapors into contactwith a cooling medium comprisingasludge containing asaturated solution ofsalt and two solidiphases of 1 said salt,,.at different degrees of st'antiallyaltering the'temperature of the heat absorbing medium.

.14..,Aprocessfof.coo1ing, which comprises pass; ins am e i i bs e ed miner e n biiawithee mucous, QmtiQ i sulphate inthe presence of the decahy drate'and; anhydrous sodium sulphate whereby heat is lab sorbed from said material in converting the decahydrate to the anhydrous form without substantially alteringthe temperature 01! the h'eat' absorbing medium, the sodiumchloride. r a

15. A method of cooling, which"co'iriiqn'ises transferring heat from the material to be cooled sludge containing also tea-sludge containing sodium chloridej and an excess of both hydrated n n drousm m sulphate."- v U 16. A'process of cooling, which comprises tirans ferring heat iromthe-material'to be cooled to a solution of sodiumearbonat'ein the presence of the decahydrate and monohydrate or sodium carbonate, the heat being absorbed converting thedecahydrate to the monohydrate withouts'ub stantiallyaltering the temperature oi-such sludge.

417. A process of coolingjwhich'comprises' trans= ferring heat from the material tobe cooled to a" solution of sodium carbonate-in -the presence of the decahydrate and monohydrate of carb'onatefthe'heat being absorbed in converting the decahydrate to the monohydrate without "substantially altering thetemperature of suchsludge;

the sludge containing also chloride-{ "18. A-process of cooling" asolution' precipitating sodium sulphate decahydrate-while simultaneous 1y converting sodium sulphate decahydrate'tothe' anhydrous salt, which comprises-introducing the solution which is to precipitate the decahydrate;

into an evaporating chambery-there subjecting the solution toevaporative coolin'gl'suitable for precipitating the decahydrate of sodium sulphate,

passing the vaporsfrom saidchaniber'into condensing contact with asludge {consisting o! a saturated solution of sodium sulphate in the presence ofexcess decahydrateand anhydrous sodiumsulphate, whereby the heat is absorbed and-the decahydrate converted to the anhydrous salt without varying the temperature orthe" cooling operation, removing the ,decahydrate from the evaporating chamber, separating it from'the-solution, and mixing thesame'with-water to supply troducing the solution which is to "precipitate the decahydrate into an'evaporating'chamber,

' there subjecting the solution to evaporativecool-;

ing suitable for precipitating the decahydrate'of sodium sulphate, passing-the vapors from-said chamber into condensing contact-with a sludge consisting of a saturated solution or sodium sulphate inthe presence 01 excess'decahydrate and anhydrous isodiumsulphate :and of chloride, whereby-theoheat isabsorbed and the decahydrate converted to; the anhydrous. salt without varying the temperaturelnoto the cooling operation, removing the decahydrate from :the evaporating chamber; separatingit from; the solu-:

' tion, mixing the same with water tolsupp ythe sludge for said cooling operation, and adding sodium chloride to'the sludge used in the cooling operation.

constantpressure below atmospheric upon evap'f orative cooling chamber, which comprisespassing the vapors from said evaporative cooling ,chamberinto a barometric;condenserfservicing said barometric condenser with a sludge of salt having no degreesoffreedom' andconta ining suf rgeeaoss ficientexcess salt" to keep saturating the con densate whereby the temperature and vapor pressure in the barometric condenser is maintained constantthroughout theoperations of absorbing heat from and condensing the'vapors. i

21. The-process of producing a salt of 'low-"de gree of hyd'rationfrom a solution containingsaid salt, which-comprises causingcrystallizationof a higher hydrate-of said salt by transferring heat from said solution to an aqueous sludge'contaim ing an excess of said higher hydrate and a substance capable of depressing the transition point of said higher hydrate-to a lower hydrate, the

absorption 'of heat by said sludge" causingthe conversion of said higher hydrate to a lower hydrate, and recovering the lower'hydrateso'produced. i

22. 'I heproc'essof producing a hydrated saltfrom a solution containing saidsalt, which comprises introducing said solution into an evapora tive cooler, creating a vacuum in said'cooler to contact with an aqueoussludge of. an excessuof;

said higher hydrate and of a substance capable of depressing the transition point of said higher, hydrateto a lower hydrated-form, the absorption of heat by said sludge causing the conversion ofsaid higher hydrate to a lower hydrated form, and

recovering thehigher hydrated form 'soproducedi 23. The process of producing anhydrous'sodium sulphatekfrom a: solution containing sodium sulphate, which comprises transferring heat from said solution.v to a sludge containing an excess, o1 sodium, sulphate decahydrate' and sodium chloride, to cause crystallization of. sodium $111:

phate decahydrate from said solution andanhydrous sodiumsulphate from said sludge, recov-' ering) the anhydrous sodium sulphate, and emplaying said-decahydrate tor the formation of the cooling sludge.

24. The, process of, V producing i:

sulphate from a solution. containing sodium sulphate, which \-comprises introducing said solution into an evaporative cooler,"'applying a -vacuumto saidxcooler-to causecoolingoi said I solutionthrough removal oiheat of fevaporation I therefromgand"thereby causing crystallization of sodium suilnhate"decahydrate, passing the vapors so produced to a barometric condenser, and bringing the same intocontact therein with a cooling chloride, the ,absorption of heat by said medium causing; the; precipitation of anhydrous; sodium eomprisinga sludge containing an ex-U cess of vsodiumgsulphate decahydrateandsulphate therefrom, and recovering ,me; latter,

and employing ,the crystallizedsodium sulphate;

as a'c'o'ndensin'g medium, the amount of said higher hydrate in said sludge being greater than willpass'into solution in the solvent at ithetem p I peratureof condensation;thetransrerenceof heat '20. A process of maintaining. asubstantially to said sludge vcausing deposition of a lower hydrate of said salt.

comprises, producing a sludge comprising'solid sodium sulphate decahydrate in anfaqueo 1.- 76

vent and bringing said sludge into contact with comprises producing a sludge comprising solid sodium sulphate decahydrate and a component capable of depressing the transition point between sodium sulphate decahydrate and. anhydrous sodium sulphate in an aqueous solvent and bringing said sludge into contact with a medium to be cooled, the amount of solid sodium sulphate decahydrate present in said sludge being sufficient to cause the deposition of anhydrous sodium sulphate upon the absorption of heat from the medium to be cooled, said deposition being a result of the conversion of sodium sulphate decahydrate to anhydrous sodium sulphate by the heat absorbed.

28. The process of producing a'jsalt of low degree of hydration from a solution containing said salt which comprises causing crystallization of ahigher hydrate of said salt by transferring heat from said solution to an aqueous sludge containing an excess of said higher hydrate and a substance capable of depressing the transition point of said higher hydrate to a lower hydrate, the absorption of heat by said sludge causing the conversion of said higher hydrate to said lower hydrate, recovering said higher hydrate so produced,

and employing same in the formation of said aqueous sludge, supplying additional refrigeration to compensate for the difference in the heatre-v quired for crystallization of the salt of higherhydration and the heat absorption capacity of said sludge to thereby form a balanced heat cycle,

and recovering the lower hydrate so produced.

29. The process of producing anhydrous sodium sulphate from a solution containing sodiumsulphate, which comprises introducingsaid solution intoan evaporative cooler, supplying a vacuum to said cooler to cause crystallization of sodium sulphate decahydrate through cooling by removal of heat of evaporation, passing the vapors from v v said cooler into contact with an aqueous sludge of an excess of sodium sulphate decahydrate, and sodium chloride, the absorption of heat by said sludge causing the conversion of sodium sulphate decahydrate to anhydrous sodium sulphate, em-

ploying the sodium sulphate decahydrate so pr'o- I duced for the formation of said sludge, supplying additional refrigeration to balance the difference in the heat absorbing capacity of said sludge and the heat required for crystallization of the sodium sulphate decahydrate and recovering the anhydrous sodium sulphate.

LEROY G. BLACK.

MORTIMER M. RICH.

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